Heat pumps explained: are they worth it?

Unlike a boiler, which burns fuel to generate heat, a heat pump moves heat from one place to another. That distinction matters: moving heat is much more energy-efficient than creating it from scratch, which is why a well-installed heat pump can deliver several units of heat for every unit of electricity it uses.

How a heat pump works

The easiest way to understand a heat pump is to think of a refrigerator — but working in reverse. A fridge pumps heat out of its insulated box and releases it into your kitchen. A heat pump does the same thing: it extracts heat from a low-temperature source outside your home and releases it at a higher temperature inside.

The key component is a refrigerant — a fluid that evaporates at very low temperatures, absorbing heat as it does so, and then is compressed to raise its temperature before releasing that heat into your heating system. The compressor is driven by electricity, but because you're moving heat rather than generating it, you get substantially more heat energy out than the electrical energy you put in. This ratio — heat output divided by electrical input — is called the Coefficient of Performance (COP). A well-designed installation typically achieves a COP of around 3, meaning three units of heat for one unit of electricity, though this varies with conditions.

Air-source vs ground-source heat pumps

The two main types differ in where they extract heat from:

• Air-source heat pumps (ASHPs) extract heat from outdoor air. They look somewhat like an air conditioning unit mounted outside the building. They're less expensive to install than ground-source, require no ground works, and are suitable for most properties with adequate outdoor space. Efficiency decreases somewhat in very cold weather, though modern units work well below freezing.
• Ground-source heat pumps (GSHPs) extract heat from the ground via buried pipes (horizontal loops in a large garden, or vertical boreholes where space is limited). Ground temperatures stay more stable year-round than air temperatures, which means GSHPs tend to run at higher efficiency — but they cost significantly more to install and require either a large garden area or access for borehole drilling.

For most homes, an air-source heat pump is the more practical and accessible starting point. Ground-source makes more sense where a larger budget allows, or where site conditions particularly suit it.

Is your home suitable?

Heat pumps can work in a wide range of homes, but they perform best — and the economics are most favourable — in homes that meet certain conditions:

• Good insulation. Heat pumps deliver heat at lower flow temperatures than a gas boiler (typically 35–55°C rather than 65–80°C). This means they need more time to heat a home, and if that home loses heat quickly, they run almost continuously. A well-insulated home retains heat well and allows the pump to work efficiently.
• Appropriate heat emitters. At lower flow temperatures, standard radiators may need to be larger to deliver the same amount of heat to a room. Underfloor heating is often ideal, as it's designed for lower-temperature operation. A good installer will assess whether your existing radiators are adequate or need upgrading.
• Outdoor space for the unit (air-source). The external unit needs to be positioned where it has good airflow and is not excessively close to neighbours (it makes a low hum).
• Hot water cylinder. Heat pumps typically heat a hot water storage cylinder rather than providing instant hot water like a combi boiler. If you currently have a combi boiler, you'll need to accommodate a cylinder.

Pros and considerations

Advantages of heat pumps:

• Low direct carbon emissions at the point of use (and as electricity grids get cleaner, the carbon footprint falls further).
• High efficiency: more heat energy out than electrical energy in, under most conditions.
• Many models can also cool your home in summer — a growing benefit as summers become warmer.
• No gas or oil combustion on-site, which improves indoor air quality and removes dependence on fossil fuel supply chains.
• Long lifespan with proper maintenance — typically 15–20 years or more.

Considerations and trade-offs:

• Higher upfront cost than a boiler replacement — this is the biggest barrier for most households.
• Running costs depend heavily on local electricity prices relative to gas or oil — this varies significantly by country and tariff.
• Best results require the system to be properly sized and installed — an oversized or poorly commissioned heat pump will underperform.
• May require radiator upgrades or other changes to the existing heating system.
• Requires a hot water cylinder, which takes up space.
• Not always suitable for flats or homes with very limited outdoor space.

How it compares to other heating systems

In general terms, across different fuel types:

• Versus gas boilers: A modern condensing gas boiler is fairly efficient (around 90%) but still burns a fossil fuel. A heat pump's carbon footprint depends on how clean the electricity grid is. In countries with cleaner grids (high renewable or nuclear share), a heat pump has substantially lower lifecycle emissions. Where grids still rely heavily on coal or gas, the advantage narrows. Running cost comparisons depend entirely on the local ratio of electricity to gas prices.
• Versus oil or LPG heating: Oil and LPG are generally more expensive per unit of heat than mains gas, and higher-carbon. In these cases, a heat pump often compares more favourably on both running costs and emissions — particularly in rural areas where gas isn't available.
• Versus direct electric heating (storage heaters, panel heaters): Direct electric heating converts electricity to heat at 100% efficiency — a COP of 1. A heat pump achieves a COP of 2–4, so it delivers the same warmth for a fraction of the electricity. If you currently heat with direct electric, a heat pump is very likely to reduce your electricity use significantly.

Incentives and running costs

Many countries offer financial support for heat pump installation — grants, subsidies, tax credits or low-interest loans. These can significantly reduce the upfront cost, and some programmes also support the cost of any necessary insulation or radiator upgrades alongside the heat pump.

Incentive schemes change frequently and vary by country, region and household circumstances. Before getting quotes, search for "[your country] heat pump grant" or "[your country] heat pump incentive" to find current programmes. Your energy supplier or local authority may also have information.

Running costs depend on how efficiently the system is installed, how well-insulated the home is, and local electricity prices. Do not rely on generic or nationally averaged figures — get quotes from multiple installers that include estimated running costs based on your specific home and local tariff.

How to get good advice and a good installation

The quality of the installation matters enormously. A heat pump that's incorrectly sized or poorly commissioned will underperform — consuming more electricity than it should, failing to keep the home warm, or both. Here's how to protect yourself:

• Get multiple quotes (at least two or three) from different installers. Be wary of anyone who doesn't carry out a proper heat loss survey of your home before recommending a system size.
• Check installer credentials. In many countries there are certification or accreditation schemes for heat pump installers (for example, MCS in the UK). Using an accredited installer is often a requirement for accessing grants, and it provides a level of quality assurance.
• Ask about radiator sizing. The installer should assess each room's heat demand at the proposed flow temperature and confirm whether existing radiators are adequate or need replacing.
• Ask about controls. Modern heat pumps run best on weather-compensation curves — the system adjusts flow temperature based on how cold it is outside. Make sure this is set up correctly.
• Check the warranty and aftercare arrangements before committing.

Before-you-buy checklist

• Get your home's insulation in good order before getting quotes — loft, walls, draught-proofing.
• Check what grants or incentives are available in your area right now.
• Get at least three quotes from accredited installers.
• Confirm each quote includes a full heat loss calculation for your home.
• Ask whether your existing radiators are adequate or whether upgrades are included.
• Confirm the system will use weather compensation controls.
• Check that space for a hot water cylinder is available or accounted for.
• Ask for estimated annual running costs based on your home and local electricity tariff.